Detect expired server certificate

[Jihwan Kim]

Hi,
I have this in my server.xml
    <Connector port="443"
               maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
               enableLookups="false" disableUploadTimeout="true"
               acceptCount="100" debug="0" scheme="https" secure="true"
               clientAuth="true" sslProtocol="TLS"
     keystoreFile="c:/j2sdk1.4.2_09/jre/lib/security/cacerts"
keystorePass="XXXX" />

cacerts is a self signed certificate.

Whewn the certificate is expired, I would like to detect it and send a
proper message to a client side user.
So, 1. how can I detect the expired cert from a Java application client.
      2. Can I detect the expired cert during the Tomcat startup?

Thank you.